An anion-controlled crystal growth route to Zn2GeO4 nanorods for efficient photocatalytic conversion of CO2 into CH4

Abstract

For photoreduction of CO2 into solar fuels driven by photocatalysis, a means to convert solar energy into chemical energy, a semiconductor photocatalyst with a specific crystal surface and high chemical stability is expected to achieve high activity and selectivity. Here, (110) facets exposed Zn2GeO4 nanorods with different aspect ratios were prepared by the ion exchange reaction between Na2GeO3 colloidal solution and various zinc salt solutions. The aspect ratio of Zn2GeO4 can be adjusted in the wide range from 2.5:1 to 20:1, depending on the acid radical. In this synthetic route, the Na2GeO3 precursor is a strong base, but strong acids such as HCl, HNO3 and H2SO4 as by-products were formed, meaning that the Zn2GeO4 single-crystal nanorods have good chemical stability in acid as well as in base. The excellent hydrothermal stability for the Zn2GeO4 nanorods in NaOH solution provides a simple method to obtain a hydroxylated surface for high performance in the photocatalytic conversion of CO2 and H2O to hydrocarbons fuels.